In some forms of Diabetic Retinopathy (DR) and Macular Degeneration (AMD), blindness results from the pathologic development of new blood vessels which are incomplete, weak and porous. The progression of these neovascular diseases is thought to occur through the production of toxic molecules, Reactive Oxygen Species (ROS). There are no long term successful therapies for such diseases which have devastating effects on patients and cost the USA over $50 billion/yr. Our long term goal is to develop a therapeutic treatment to protect the health and function of retinal cells and thereby prolong vision and improve the quality of life for patients with DR or AMD. Because the excessive rise in ROS occurs upstream of most other retinal pathologies, it represents a common node which can be targeted by antioxidants and other molecules which increase the expression of Phase II antioxidant enzymes. Our published and preliminary data show that cerium oxide nanoparticles, which catalytically destroy ROS, can prevent development of pathologic choroidal and retinal neovascular lesions and cause the regression of existing pathologic neovessels in the Very Low Density Lipoprotein Receptor null retina by modulating the expression of many retinal genes including Vascular Endothelial Growth Factor (VEGF). Our central hypothesis is that cerium oxide nanoparticles, because of their catalytic antioxidant activity and long term retention in the retina, will continuously scavenge ROS and inhibit pathologic neovascularization over prolonged times -up to 12 months. Specific aim 1 will determine duration of nanoceria in the retina and the extent to which they retain activity against neovascularization. Inductively coupled plasma mass spectrometry will quantitate cerium at the parts per billion levels. Fundoscopy, electroretinography and optical coherence tomography will be used for longitudinal studies on the same animal to evaluate neovascularization, retinal function and thickness of the outer nuclear layer. Nanoceria effects on specific genes involved in oxidative stress, inflammation and neovascularization will be analyzed using confocal microscopy, Western blots and PCR arrays. Specific Aim 2 will demonstrate that nanoceria provide protection to the retina by reducing the effects of oxidative stress on photoreceptors and Retinal Pigment Epithelial (RPE) cells. Gene activity, proteins and structures indicative of photoreceptor- and/or RPE- oxidative stress will be evaluated. Specific Aim 3 will test the hypothesis that the combinatorial use of nanoceria and sulforaphane, an inducer of Phase II antioxidant enzymes, will result in an additive or synergistic effects in the Vldlr retina. Expected outcomes - the work proposed is expected to demonstrate the longevity, potency and mechanisms by which nanoceria inhibit pathologic neovascularization in the retina. The results are expected to have an important positive impact because the demonstration of the long term effectiveness of the nanoceria will most likely support their therapeutic use and changes in activity of identified genes should provide additional targets important for treating DR, AMD and other diseases which involve oxidative stress.